Taper leaf spring blank

ABSTRACT

Taper leaf spring blank generally rectangular in cross-section and having upper and lower stress surfaces with flash resulting from the rolling operation extending along the low stress areas along the sides of the blank.

United States Patent [191 Poulos [451 Dec. 10, 1974 TAPER LEAF SPRING BLANK [75]" Inventor:

[73] Assignee: Spectra McIntosh Corporation,

Chicago, Ill.

May a, 1970 Gus L. Poulos, Winamac, Ind.

[22] Filed:

[21] Appl. No.: 35,705

521 U.S.Cl 267/47, 29/173, 72/198 51 Int.Cl. ..F16f1/1.8,B60gl1/02 [58] Field ofSearch...,. 267/47; 29/173; 72/197,

[56] References Cited UNITED STATES PATENTS 1,993,883 3/1935 Heddonni 72/198 Archer 2,364,610 l2/l944 72/198 2,608,752 9/1952 Schilling 267/47 3,145,984 8/1964 Hallam .267/47 3,354,682 11/1967 Dupuy 72/198 3,547,462 12/1970 Stamm 267/47 Primary Examiner-Drayton E. Hoffman Attorney, Agent, or FirmHill, Gross, Simpson, Van

Santen, Steadman, Chiara & Simpson [57] ABSTRACT Taper leaf spring blank generally rectangular in crosssection and having upper and lower stress surfaces with flash resulting from the rolling operation extending along the low stress areas along the sides of the blank.

1 Claim, 7 Drawing Figures TAPER LEAF SPRING BLANK BACKGROUND AND OBJECTS OF INVENTION Tapered leaf springs have heretofore been rolled by placing a hot spring blank on a die, extending along and secured to a reciprocating table, and by exerting pressure on the blank and die by a work roll driven at the linear speed of reciprocation of the blank. The spring blank is confined from lateral spreading between side plates or dies, to restrict side flow of the hot blank during the forming operation. The die is so formed as to shape the blank into a tapered leaf spring form, upon the exertion of pressure on the blank by the work roll, during rotation of the work roll and reciprocation of the table and die.

With such rolling processes, flash is left along a stress area of the spring. The flash extending along the upper or lower edges of the spring, creates stress risers with many resultant fatigue problems. The spring is thus likely to fail along a stress riser, many times upon very little use of the spring.

A principal object of the present invention is to provide a new and improved taper leaf spring blank in which all flash or irregularities in the spring blank are in reduced or non-stressed areas of the spring.

Another object of the invention is to provide a new and improved taper leaf spring blank so constructed that the blank is in the form of a substantially finished spring requiring no machining to remove irregularities in the stress areas of the spring.

Other objects, features and advantages of the invention will be readily apparent from the following description of a certain preferred embodiment thereof,

taken in conjunction with the accompanying drawings,

although variations and modifications may be effected without departing from the spirit and scope of the novel concepts of the disclosure.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic end view of a roll stand which may be utilized to roll a spring blank into a taper leaf spring form.

FIG. 2 is a diagrammatic view illustrating two cooperating rolls having cavities extending along the faces thereof formed to confine a hot blank from side flow of the metal during the forming operations and to form the blank into a tapered form free from irregularities in stress areas of the spring.

FIG. 3 is a diagrammatic view in end elevation of the rolls shown in FIG. 1, showing a spring blank between the rolls.

FIG. 4 is a fragmentary diagrammatic plan view of one half of a rolled spring showing flash extending from the neutral areas of the spring; and

FIGS. 5, 6 and .7 are sectional views taken respectively along lines V-V, VIVI and VII-VII of FIG. 4.

DESCRIPTION OF PREFERRED EMBODIMENT OF THE INVENTION In the form of the invention diagrammatically illustrated in the drawings, I have schematically shown in FIG. 1 a roll stand 10 including a frame having columns 11,11 extending upwardly from opposite sides of a base 12, and connected together at their tops by a cross bar 13. Vertically disposed hydraulic cylinders 15,15 are mounted on and depend from the cross bar 13 and have substantially in engagement with each other during the g piston rods 16,16 suitably attached to hearing yokes 17,17 forming bearing supports for bearing assemblies (not shown) for a roll 19. The roll 19 has a die 20 extending therealong for a portion of the circumference thereof. The roll 19 may be driven from a drive shaft 21 through a suitable universal coupling such as a roller mill coupling, commonly used for driving the rolls of roller mills. The drive shaft 21 may be connected by means of a universal joint or roller mill coupling (not shown) to a drive motor (not shown), to positively drive said roll 19 from any convenient power source at the rate of speed of the speed of a cooperating lower backing roll 23.

The lower backing roll 23 has a die 24 extending circumferentially therealong for a portion of the circumference of the roll, and shown in FIG. 2 as exactly like the die 20, and driven so that like parts of the dies 20 and 24 are in registry with each other during the entire rolling operation. The roll 23 is journalled in suitable bearing supports 25,25 extending upwardly of a table 26 supported between the side frame members 11,11. Suitable bearing assemblies (not shown) are journalled in the bearing supports to form bearings for the roll 23 journalling the roll for rotation with little, if any, deflection during the rolling operation. A shaft 22 extends from the roll 23 and may be driven from the power means driving the shaft 21, to effect rotation of the rolls l9 and 23 at the same rates of speed and to effect exact registry of the dies 20 and 24 with each other during the entire rolling operation.

The die 20 is shown as being in the form of a segment of a circle suitably secured to the face of the roll-l9 and extending radially therefrom and circumferentially thereabout for a portion of the circumference of said roll 19. The die 20 has a die cavity 27 extending therealong opening to one end of said die and having parallel spaced side walls 29,29 extending radially outwardly of a die face 30 of said die. The die face 30 may be a generally spiraling die face taper machined in the die to produce a straight line taper of the spring from a thickened mid portion of the spring to the end thereof. The taper of the die face 30 may be of a generally spiral form or may be formed from one or more uniformly connected arcs struck from centers offset from the center of rotation of the roll 19.

The die 24 is exactly like the die 20 and has a die cavity 31 extending therealong for a portion of the length thereof and having parallel side walls 32 confining the hot metal during rolling thereof.

The lengths of the die faces of the cavities 30 and 31 are such as to taper roll a heated spring blank from a mid portion of the blank to the end of the blank during a single pass of the blank between the dies 20 and 24.

It may be seen from FIGS. 2 and 3 that the semi-circumferential peripheral faces of the dies 20 and 24 are rolling operation and come into engagement with each other midway between the top and bottom sides of the spring blank to minimize flash and to confine any flash to the minimum or non-stressed areas of the spring, along the sides thereof between the top and bottom surfaces of the spring.

In carrying out the rolling operation and method diagrammatically illustrated in the drawings, a metal spring blank 33 in the form of a flat bar of spring steel is heated as by induction heating or any suitable heating process to a preselected hot rolling temperature. The die 20 being separated from the die 24 by operation of the hydraulic cylinders 15,15, the two rolls 19 and 23 are rotated into positions with the open ends of the dies in general alignment with a diametral line extending through the diameters of said rolls or any other initial position which may be indicated on the rolls or a suitable fixture (not shown). With the dies 20 and 24 separated, the blank heated to hot rolling temperature is placed in the registering die cavities 27 and 31, midway between the ends of the blank. Fluid under pressure is then admitted to the hydraulic cylinders 15,15, bringing the die cavities and die faces thereof into rolling engagement with both sides of the blank and con- Power is then'applied to the two rolls to drive the rolls at the same rates of speed and to advance the blank along the die cavities from the open end thereof toward the radially outwardly tapering faces of the die face 30. Upon rolling the spring to the shallow ends of the cavities 27 and 31, the roll 19 is separated from the roll 23 by the application of fluid under pressure to the piston rod ends of the hydraulic cylinders 15,15. The unfinished end of the blank may be reheated and the hot blank may then be reversed. The rolls 19 and 23 may then be rotated to position the deepest parts of the die cavities at a mid portion of the spring blank. The spring blank may then be placed in the die cavities, with the mid portion of the blank spaced from the center of the blank a distance sufficient to form a uniform thickness portion of the blank for attachment to a spring seat. Pressure may then be applied to the cylinders 15,15 to force the die 20 toward the die 24. The two rolls l9 and 23 may then be driven to form the opposite ends of the spring.

It should be understood that the present method is described for rolling a single leaf spring in which opposite ends of the spring taper from the center or a flattened securing end portion of the spring and that when doing this, first one end of the blank is rolled, the unfinished end is reheated and the blank is then reversed to roll its other end. The position of rolling from the mid point of the blank may be accurately determined to provide an intermediate connecting or seat portion of the spring to be seated on a conventional spring clamp assembly. A cantilever type of leaf spring, however, may be attained by rolling the blank from one end thereof.

1f the bar to be rolled is of such length that it does not exceed the circumference of the die, then a bar tapered at both ends may be rolled in a continuous operation.

It may further be seen that the workpiece or blank 33 to be rolled to shape is disposed between the rolls 19 and 23 and the cavities 27 and 31 of the dies, in such a position that the dies substantially meet when rolling pressure is placed on the rolls, with the walls of the cavities extending along opposite sides of the blank and meeting intermediate the top and bottom edge faces of the blank. The walls of the cavities thus confine the blank from lateral flow and attain a completed spring free from flash along the top and bottom edges of the spring.

FIG. 4 diagrammatically illustrates a fragment of a portion of a completed spring 36 and shows flash 37 extending from opposite sides of the spring between the top and bottom edges thereof. FIGS. 5, 6 and 7 show in section at various locations along the rolled spring 36 that the flash or irregularities in the rolled spring are between the top and bottom edges of the spring in the minimum or non-stressed areas of the spring.

It should further be understood that the lengths of the die surfaces of the dies 20 and 24 are shown in an exemplary form only, and may be taper machined along various contours to provide a finished product having a required uniform taper necessary to roll a finished leaf spring product to a uniform straight line taper, free from flash along the tensile and compressive edges of the spring. It should further be understood that the lengths of the die cavities are such as to form one half of the spring in one rolling operation, and that the linear speeds of the rolls l9 and 23 are so related to the lengths of the die cavities as to enable one half of the spring to be formed in a single pass.

it should further be understood that with the present rolling operation the section thickness or density of the metal along the spring leaf may be accurately controlled, to form a spring with the desired taper and that the walls of the cavities, meeting intermediate the top and bottom surfaces of the blank, hold the spring blank from side spreading and position any flash that may be formed in the blank out of the stress areas of the finished spring 1 claim as my invention:

1. A tapered leaf spring blank generally rectangular in cross section and having upper and lower high stress surfaces and side edges between said high stress surfaces deflning low stress areas of the blank having flash located between the upper and lower high stress surfaces of the blank along the low stress areas along the sides of the blank. 

1. A tapered leaf spring blank generally rectangular in cross section and having upper and lower high stress surfaces and side edges between said high stress surfaces defining low stress areas of the blank having flash located between the upper and lower high stress surfaces of the blank along the low stress areas along the sides of the blank. 